The present invention relates to a process utilizing a solution containing sophorosides, said process being adapted for cleansing hydrocarbon-impregnated solid particles. This process is more particularly intended for washing oil well cuttings.
In the field of oil drilling, the cuttings pulled out by the tool are taken up to the surface by the upflow of the drilling fluid injected through the channel of the drill string. Drilling fluids containing hydrocarbons are very commonly used to solve drilling problems in formations reactive in the presence of water, for example some clays or salt. The drilling fluids suited to high temperatures may also be based on mineral oil. Particularly, in the North Sea, about 75% of the wells are drilled with oil-based fluids. In these cases, the cuttings coming up to the surface are impregnated with a relatively large amount of hydrocarbons.
Discharge of these impregnated cuttings is generally regulated by the local authorities.
More particularly, in offshore drilling operations, discharge of such cuttings is no longer allowed until they have been subjected to an additional treatment to conform to current standards. The operator thus has to face the following choices:
not to use drilling fluids containing hydrocarbons any longer, PA1 to transport the polluted cuttings on shore to subject them to a specific treatment before discharge, PA1 to cleanse the cuttings so as to be able to discharge them at sea. PA1 bactericidal agents when the product appears in the lactone form, PA1 emulsifying agents in the farm-produce industry (U.S. Pat. No. 3,622,344) and hydrating agents in the cosmetic industry (U.S. Pat. No. 4,305,961). In these applications, the product appears in the ester form. PA1 the diversity of the possible sophoroside structures provides a high flexibility of use and makes them easily adaptable to a specific application. This is explained hereafter in the description of the sophorosides; PA1 sophoroside compounds are not toxic. Moreover, their innocuousness allows their use in the farm-produce industry and in cosmetology; PA1 they are entirely biodegradable; PA1 they are stable notably in alkaline medium, unlike sugar esters. Drilling fluids are generally alkaline; PA1 the fermentation manufacturing process disclosed by application FR-90/16,211 enables good efficiency rates to be obtained; PA1 the raw materials, sugars and fatty bodies, are little costly and easily available. PA1 partial or total deacetylation of the sophorose group, PA1 partial or total delactonization. Delactonization consists in the opening of the lactone cycles (formula (2)), which liberates the carboxylic acid group, PA1 esterification of the carboxylic acid group through alcohols whose structure and molecular mass also constitute parameters for adjusting the properties. For example, according to patent U.S. Pat. No. 4,297,340, the HLB value ranges from 6 (lipophilic surfactant) to more than 20 (very hydrophilic surfactant) when the alcohol used for the esterification has a number of carbon atoms passing from 18 (stearylic alcohol) to 1 (methyl alcohol).
The first two choices may not be viable for technical and/or economic reasons. It would thus be advantageous to use the third technique while having an efficient and economical means for washing the cuttings on site.
Document EP-A-0,330,379 notably describes an aqueous solution intended for cleansing oil-impregnated surfaces, for example drill cuttings.
But this document does not recommend the use of sophorosides.
Documents U.S. Pat. No 4,645,608 and EP-A-0,084,411 also describe methods for washing cuttings and recommending formulations containing mainly solvents and surface active agents or surfactants. None of these two documents envisages using sophorosides.